Behaviour of Blind Bolted Moment Connections for Square HSS Columns

Abstract

<p>Although hollow structural sections (HSS) are an efficient structural member and have attractive architectural appearance, their use as columns in low or medium-rise moment-resisting steel frames has been limited. Some of the difficulties are due to the lack of a simple and practical field-bolted moment connection between a W-shape beam and an HSS column.</p> <p>The objectives of this research study are to develop a practical bolted moment connection between a W-shape beam and a square HSS column and to evaluate its behaviour experimentally under monotonic and cyclic loading. In addition, it is of interest to evaluate the effect of the developed connection response on the frame's overall behaviour, and provide guidelines and design rules for detailing the connection. In this research study, attention is focused on investigating the behaviour of bolted end-plate connections developed by blind fasteners. An experimental-analytical approach was used in this research program.</p> <p>The experimental program which was carried out on full scale beam-to-column connections involved three phases. First, three monotonic tests were conducted to examine the behaviour of such a connection using blind fasteners and to compare their response with a similar connection using high strength A325 bolts. Second, four tests were conducted on connections utilizing larger HSS columns and with different stiffening conditions to reveal different modes of failure. Third, two cyclic tests were performed to examine the effect of cyclic loading on such a connection.</p> <p>Based on the observations and results of the experimental program, an analytical model to predict the behaviour of the connection was developed. The sensitivity of the model was checked by comparing its predictions with the experimental results. The model was then incorporated into "Drain-2DX" computer program to be used in analyzing moment resisting frames. Based on both experimental and analytical results, a design procedure for the connection was proposed.</p> <p>The effect of connection flexibility on the response of a 4-storey steel moment frame was evaluated by comparing the response to that of a similar frame with rigid connections. The frames were analyzed statically under monotonically increasing loading and dynamically under two earthquake ground motions. It was concluded that, the flexibility of semi-rigid connections should be included in both static and dynamic analyses to determine a frame's structural response more realistically.</p>